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Old 11-10-2007, 11:51 AM
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Originally Posted by Super Blue F350
what is the advantage to this please explain I just picked up my 08 PSD tonight and I need all the help I can get
Originally Posted by pbeering
It runs the Engine RPM's up to support a PTO, air compressor, or to compensate for a big electric draw (think ambulance or fire apparatus with lots of lights)
In addition to the items pbeering, referred to, the main reason it is done by most PSD owners is to prevent wet stacking during extended idle times (longer than 10-minutes), and with the new emissions controlled diesel engines with an EGR system it helps prevent deposits and sticking of the EGR valve do to exteneded idling.

When a diesel engine idles it actually cools off (unlike a gas motor), diesel engines are not efficient when they are cool and incomplete combustion occurs resulting in deposits forming in the cylinders, on the valve stems (leading to sticking valves), EGR valve, VGT turbo vanes etc. Also do to the low engine temperatures as a result of extended idling, there is more unburned fuel which can wash down the cylinder walls and end up in the crankcase, diluting the oil and reducing the oils lubrication properties.

If you are going to idle your PSD for 10 minutes or more at a time you should do so at an elevated idle, to help eliminate these problems. Also if you hook up the high idle mod through the BCP circuit it will monitor the batteries and increase the idle to keep them fully charged.

The best approach to idling a diesel engine, especially modern ones with emissions control systems, is to idle as little as possible. You are much better off to just turn the motor off instead of letting it idle for extended periods.

As far as letting the truck and engine warm up before driving off, you are much better to not let it idle longer than a couple of minutes and just slowly drive off for the first couple of miles while things warm up. FMC has also programmed the PCM on the 6.0 & 6.4 to elevate the idle (Cold Weater-Idle up stategy) on a cold engine that is idling, to help reduce these problems.

"The diesel engine contains a unique, Cold Weather Idle up feature,calibration strategy within the Powertrain Control Module
(PCM). Under the appropriate conditions, the strategy will automatically elevate the engine idle speed after 130 seconds of idling
in cold ambient temperatures. For this feature to be activated the
truck must be in P (Park) (for automatic transmission), in neutral (for
manual transmission) with the park brake applied and engine oil
temperature below 158F (70C). This strategy raises the rpm to a level that reduces the potential to produce Coking or Wet Stacking,
which is common to all diesel engines when idling for extended
periods during cold ambient temperatures."
From the FMC "Diesel Supplement Manual"

Last edited by blackhat620; 11-10-2007 at 11:54 AM.
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